The invention relates to instruments for use with a bone anchor with a cannulated shaft and a plug member which is insertable into the shaft for closing the shaft at one end. The instruments include an injection cannula, a plug member introducing device, a metering device, a depth control device, a plug member supplying device and a plug member storing device. The bone anchor and the instruments are particularly suited for use in minimally invasive surgery (MIS).
WO 01/26568 A1 describes a bone anchor in the form of a bone screw with a screw head and a threaded shaft which includes an axial bore and a plurality of radial bores. The axial bore is open at the screw head side and closed at the free end of the screw shaft. The known bone screw can be anchored in the bone through injecting bone cement into the shaft. This leads to a permanent and safe fixation of the bone anchor.
A bone anchor in the form of a bone screw with a cannulated shaft is also known from U.S. Pat. No. 5,047,030. The interior of the bone screw has a continuous longitudinal canal with several radially extending transverse canals which contact the longitudinal canal. The longitudinal canal is open at both ends of the screw, and it is possible to connect a vacuum pump via a tube in the area around the screw head to apply a vacuum to suck blood or other material.
WO 02/38054 A2, US 2004/0122431 A1 and US 2004/0147929 A1 disclose bone screws with a tubular threaded portion and a tip portion which can be connected to the tubular threaded portion. The tubular threaded portion has a number of recesses in its wall. It is possible to fill the tubular threaded portion with bone cement.
Minimally invasive surgery is applied in an increasing number of cases. With minimally invasive surgery in some cases guide wires are used to place an implant at the implantation site. A minimally invasive access is usually made percutaneously through the skin.
Based on the above, there is a need to provide a bone anchor which has a broad range of application, for example which is suitable for being placed at the implantation site with minimally invasive surgery and which can be filled with a bone cement or another substance. Additionally, there is a need to provide instruments for use with such a bone anchor which allow convenient and safe hand-ling.